The present invention relates to a diaphragm carburetor for an internal combustion engine that operates with scavenging, especially for the two-cycle engine in a manually-guided implement, such as a power chainsaw, a cut-off machine, a trimmer, a brush cutter, or the like.
DE 199 18 719 A1 discloses a diaphragm carburetor, the butterfly valve of which is coupled with the air valve. The butterfly valve can execute an idle path relative to the air valve. The butterfly valve and the air valve can be coupled via a linkage. With this type of coupling, the butterfly valve and the air valve open linearly after passing through the idle path. Another embodiment provides that the butterfly valve and air valve be coupled via levers that have a cam contour. By means of the cam contour, a desired opening characteristic of the air valve is to be achieved as a function of the position of the butterfly valve. However, the manufacture of such a cam contour is complicated. Already slight deviations from the desired dimensions of the cam contour lead to relatively large variations of the opening characteristic.
It is therefore an object of the present invention to provide a diaphragm carburetor of the aforementioned general type that imparts to the internal combustion engine a favorable ratio of the fuel/air mixture to clean air, and that is easy to manufacture.